Signalling system



Oct. 7, 1947. J. E. LIN DBERG, JR., EI'AL 8,

SIGNALLING SYSTEM Filed May 18,1942

INVENTORSZ Powsi 1 s'awzcz 60/ AMPLIFIL'P s/smu auras 6 JOHN E. LINDBERG J2. Beooxs WALKER ATTORNEK Patented Get. 7, 1947 John n. Lindberg, Jr., Lafayette, Calif., and

Brooks Walker, Arlington, Va.

Application May 18, 1942, Serial No. 443,516 a 12 Claims.

One of the general objects of this invention is to transmit intelligence between points in such a manner that unauthorized persons or the enemy cannot pick up such signals, as between ships in convoy, battleships in enemy territory, airplanes in flight, between each other or between planes and ground, detachments of ground troops, etc. An object of this invention is to provide means whereby signal communications, such as dot and dash or other means of transmitting intelligence, may be conveyed from one point to another, preferably by the use of black the fluorescent screen so that the direction of station I from station 2 can be readily determined by the portion of the fluorescent screen that is energized into visible distinction, or by focusing the light on a designated portion of said screen, and by other means as hereinafter disclosed.

A further object of the invention is to provide means for concentrating the radiant energy from point I, as received on a given area at point 2, concentrating the energy as by a lens and/or a reflector, and applying this concentrated energy to a reduced area of the fluorescent screen.

Another object is to provide a transparent fluorescent screen in which the illumination of the fluorescent face can be viewed from the backside of the screen to make direction indications and/or signal reading easier.

Another object of the invention is the use of a relatively invisible source of light energy, such as black light, from one point, directing same towards a second point where it is picked up and preferably concentrated on a photo-cell detector, amplified and made intelligible either by the use of light, sound, etc., so that signals from one point can be transmitted to the second point with practically no danger of detection by the trated the invention by way of example in the accompanying drawings in which:

Figure 1 is a diagrammatic view, partly cut away, illustrating one form of the invention,

using a fluorescent screen pick-up.

Figure 2 is a diagrammatic view, partly cut away, of an alternate form of receiving device which could be used in connection with Figure 1,

Figure 3 is a side view of the fluorescent screen, as viewed from the back when not pointed directly at the source of light, with the light concentrated as in Figure 2.

Figure 4 is a view similar to Figure 3 but with the detector pointed at the source of light.

Figurefi is a diagrammatic view illustratin another form of the invention, utilizing a radiant-energy-sensitive cell pick-up. Figure 6 is an'end view illustrating the appearance of the fluorescent screen, as viewed in Figure 1, when the detector is pointed at the source oflight.

Figure '7 is similar to Figure 6, and illustrates the appearance of the fluorescent screen when the detector is not pointed directly at the source of light.

Figure 8 is a view of an alternate form of fluorescent, screen, as might'be used in Figure 2.

Figure 9 is-a side angle elevation view, partly cut away,,of an alterante type of detector, embodying a reflector to concentrate the light on the fluorescent screen.

Figure'IO is an alternate form of the invention as applied to a vehicle.

In all figures, like numerals of reference refer to corresponding parts in the various drawings.

In Figure l we have a source of electrical energy Ilka signal key I l, and a light bulb [2 of the heated filament type capable of rapid enough action to be used for signals, or of the gas type which is capable of very fast action. This light is preferably of the ultra-violet or black light type, which is substantially invisible in relative darkness or has a relatively short range of visibility. A reflector I3 and lens l4 suitably concentrates and directs the rays from bulb l2 through shroud 15 from station Pl towards station P2 where a detector unit is located consisting of a shrouded hood 20, a fluorescent screen 25 which may be mounted on a transparent plate 26 with a viewing shroud 20A, projecting rearward therefrom with an eye opening 203 in the rear thereof to cut ofioutside illumination from the back of the transparent plate 26 so as to view better the action of the fluorescent face 25. In case it is 'desired to view the fluorescent screen from the energized face, view detector 200 is provided in "which a transparent plate 29 may cover the opening and a shutter 21 may be operated by handle 28 to normally cover the opening formed by 200 to exclude light from getting in to the fluorescent screen except When a view is desired of the front face of the fluorescent screen 25 as through transparent material 26. Sights 33 and 3| may be provided so as to determine the location of the light source at Pl from P2 when the detector P2 is in proper alignment therewith, as determined by the amount of fluorescent screen 25 which has been energized. Due to the shroud 2B which has substantially parallel sides, the fluorescent screen 25 will only be fully energized when shroud 28 is pointed directly at the light source. The opening in the shroud should be substantially the same size and shape as the screen 25. If the fluorescent screen as viewed through the sight-hole 20B is completely illuminated, the operator knows that the instrument is sighted at the light source and by use of the sights 35 and 3|, can determine the direction of the light source. Signals such as dot and dash can now be transmitted by use of key II from the light source to the fluorescent screen which can be viewed by the receiver to pick up such signals without danger of the enemy being aware of such signals being given which would be the case with radio or normal blinker light communication. If the detector is not pointed directly at the source of light, only a portion of the screen will be illuminated, as illustrated in Figure '7, and when the detector is pointed directly at the source of light, the sides of the shroud 20 will point at the source of light also and will not shade any portion of the fluorescent screen so that the entire fluorescent screen 25 will be energized into distinction, as illustrated in Figure 6.

In Figure 2 we have shown a modification of the invention wherein the light is picked up by lens ii] and focused on the fluorescent face 25 of the transparent backing 26 to thereby concentrate the light energy which falls on said lens from the source .onto a relatively small portion of the fluorescent screen. This is desirable where the distance between point PI and point P2 and the intensity of the light source may be such that the fluorescent material at point P2 might not be sufficiently energized by direct radiant energy from P! without concentration of the radiant energy on the fluorescent face. A nontransparent fluorescent screen could be used with the concentrating lens, as described, by viewing from the front face in a manner similar to that described in connection with Figure 1.

The fluorescent screen may be suitably marked at its center with a target circle or other suitable marking so that when the focused energy from the light source through lens 40 falls at the center of the screen as shown in Figure 4, the operator knows that the pick-up instrument at station P2 is in line with the light source, as can be determined by sights 30 and 3| on this instrument.

When the detector is not pointed at the source of light, the focused energy from the source will fall on the fluorescent screen away from the centering circle, as illustrated in Figure 3. As shown, the energized portion of the screen 25 indicates that the light source is below and to the right of the axis of the sights 3H and 3 I.

Figure 8 illustrates a further modification of the screen which may be used in connection with the detector shown in Figure 2, wherein the center of the fluorescent screen is left blank or formed of material that will be energized into fluorescence of a distinguishing magnitude or color from the balance of the screen, so that when the detector is pointed correctly at thesource of'light, the fluorescent screen will appear as shown in Figure 8 with a ring of one color energized into distinction with a center circle or other suitable shape appearing as a blank or as another color suitably distinguishable. Or when centered, the energized spot could be a ring with a blank hole or could be a blank except when off center. Where a blank spot is used at the center of screen 25 as a centering indication, it will also serve as a sight by looking through the eye hole and through the blank centering hole similar to circle gun sights. A center marking likewise could be of material to be energized into a variation in intensity of the same color as the surrounding circle when exposed to the same magnitude of energization as that imposed on the surrounding circle.

A manually adjustable screw 43 may be provided to adjust the focus of lens 40 relative to the fluorescent face 25 by moving shroud 42. which supports the lens, relative to shroud 4| which supports the fluorescent screen 25 and its transparent backing 26. A viewing shroud 45 may be provided to cut out auxiliary light and make viewing of the fluorescent screen through the transparent support 26 easier.

With this detector instrument, the dot and dash or other signal will be viewed only on the illuminated concentrated spot of the fluorescent screen but this will be ample to transmit readily such intelligence.

In Figure 5 we have a power source 50, a signal key 5|, a black light bulb source 52, a reflector 53, and a signal shutter 54 at one station and a receiving unit at the other station consisting of a lens suitably adjusted by knob 6| so as to focus the picked up light or energy on detector cell which may also have a concentrating reflector 66, or the reflector may replace the lens. The housing for this mechanism may carry suitable sights 30 and 3| to determine the direction of the light source from the receiving source when properly focused or for use in focusing the pickup fluorescent plate when the source of light is known. The energy from the pick-up cell 65 is preferably amplified and goes to a signalling device which can be either .of a visible type, sound type, or other suitable mechanism for transmitting intelligence and may be provided with .a galvanometer '61 to indicate the intensity of the signal as picked up which can be used in determining the distance and/or direction of the source of light from the pick-up mechanism, as when the intensity is .the greatest, the pick-up mechanism will .be directed at the source of light. This circuit could be similar to a light meter, with said pick-up at the concentrated focal point of the lens when correctly sighted or, at the end of a shrouded tube, the maximum reading of the meter would indicate correct pointing of the receiver toward the light source. When correctly pointed at the light source and the reading compared to a standard, it would give an indication of distance, particularly if the source was a standard power.

In the mechanism as disclosed, a fluorescent screen can be so made to be primarily sensitive to the black light source only and relatively independent of other light such as daylight, so .that pick-up can be obtained under conditions of daylight or darkness. Likewise, the photo-cell pickup can be of a suitable type that will be sensitive primarily to the black light source as differentiated from outside light; however, it will probably work best under conditions of reduced outside light. In Figure 5 it will not be necessary to use both the keying mechanism 5| and the shutter 54, as in some cases the key 5] may be the switch to energize bulb 52 which may be of the filament type or arc type of slow-acting character, the beam from which may preferably be controlled by the shutter 54 as is used with visible blinker lights at present. If the filament is of the gas type or the sufficiently f ast-acting heated filament type or are type, the shutter 54 can be done away with and the key 5! used, similar to the construction illustrated in Figure 1.

Figure 9 illustrates another form of detector construction in which a shroud it! supports a transparent screen 15 having a face 75A suitably treated with fluorescent material and having suitable means of distinguishing when the'energy from the light source, as concentrated by the rear reflector 12, is correctly focused at the center of the fluorescent screen 15A in some such manner as described in connection with Figure 8. A viewing hole 12A is preferably formed in the reflector screen so that the operator may view the fluorescent screen to pick up the signals and to determine when the detector is pointed directly at the source of radiant energy.

In Figure we have illustrated another form of the invention as applied more particularly to a vehicle such as an airplane, automobile, boat, or other form of transportation, where a windshield of transparent material 88 is located between the operator and the direction in which the vehicle is traveling. A reflector 8! is preferably so located that it will pick up radiant energy from the source cf light, such as illustrated in connection with Figure 1, and concentrate the radiant energy after reflection on a point within the range of view of the operator either on the windshield as shown, in which case that portion of the windshield is preferably treated with clear material having fluorescent characteristics so as to be energized into visible distinction by the concentrated rays from the radiant source; or, if a second reflector 82 is used and properly focused, the concentrated energy from both reflectors will fall upon the fluorescent screen and when the fluorescence resulting from the radiant energy reflected by reflectors SI and 82 coincides, it will indicate that the source of the radiant energy is directly ahead of the vehicle, provided the angle of the two reflectors is set accordingly. It is to be understood that the fluorescent screen might be a non-transparent screen in the vicinity of the windshield near the perimeter thereof either above or below or at either side or adjacent the operating instruments, or other suitable location. As a further means of distinguishing the energy from the two screens, they might be composed of difierent material or of different reflecting character or of different color so that the fluorescence resulting from energy reflected from each would appear of a different magnitude and/or different color to assist more easily in the difierentiating between them when endeavoring to determine the direction of the source of light such as would be necessary in using this device as a homing mechanism for a plane in conditions of poor visibility or black-out landings in case of war. In such cases, the source of radiant energy would originate from a suitable location in the airport, possibly near where the plane is supposed to land and the location of the ene'rgized portion of the fluorescent screen energized by the light from the reflectors 8| and 82 would indicate the direction of the desired landing point from the plane. The magnitude of 6 the intensity of the illumination of the fluorescent screen so energized might be a measure of the distance of such homeport from the plane, by comparing it with standard, fixed colors in a chart or by the use of a light meter focused on the energized portion of the fluorescent screen.

Obviously, with any of the systems described in connection with this invention, signals and intelligence can be transmitted from the light source to the operator and the receiving device by dot and dash, intensity variation, or other suitable fluctuations of the light source.

At various times, we have used the term black light or light of substantially invisible character; by this we mean light energy essentially difierent than the light energy of the luminous field, with best results possibly obtained in the ultra-violet field.

Other objects of this invention will be more particularly pointed out in the following claims. We also wish to point out that We do not wish to limit ourselves to the exact details or modes of operation set forth in this application and drawings, for it will be obvious that wide departure a may be made in the way of details without departing from the spirit and scope of our invention, which is as set forth in the following claims.

We claim as our invention:

1. A vehicle having a windshield of transparent material, part of said windshield being fluorescent and luminous when energized by concentrated black light, a black light source remote from said vehicle a collector and concentrator for said light on said vehicle, and means for transmitting intelligence to the operator of said vehicle by the portion of said fluorescent screen that is energized by said concentrated black light, said part of said windshield that is fluorescent having an indicator upon which the concentrated light targets when said vehicle is pointed in the direction of said source.

2. A vehicle having a windshield screen capable of being energized into visible distinction by black light, a source of black light remote from said vehicle, and means on said vehicle for receiving a. portion of said black light and concentrating it on a portion of said screen, the por tion of said screen energized by said black light having markings thereon to indicate the direction of said source of black light from said vehicle.

3. A vehicle having a screen capable of being energized into visible distinction by black light a target formed in said screen, a source of black light remote from said vehicle, means on said vehicle for receiving a portion of said black light and concentrating it on a portion of said screen, the portion of said screen target energized by said black light indicating the direction of said source of black light from said vehicle, and means for columnating said source of black light to further indicate a desired direction from said source of black light as picked up on said vehicle,

4. A vehicle having a screen capable of being energized into visible distinction by black light, a source of black light remote from said vehicle, and means on said vehicle for receiving a portion of said black light and concentrating it on a portion of said screen, the portion of said screen energized by said black light indicating the direction of said source of black light from said vehicle by a distinctive marking on said screen, said vehicle having a transparent windshield, said screen being on a portion of said windshield, and said screen being transparent when not energized.

'5. A vehicle having a screen capable of being energized into visible distinction by substantially invisible light, a source of'said light remote from said vehicle, and means comprising a shroud for said light of about the same'size and shape as said screen to concentrate said light on only a portion of said screen when said vehicle is not pointed directly in the direction of said source, the relationship of the portion of said screen energized by said light to a point fixed with relation to said screen indicating the direction of said source from said vehicle.

6. Apparatus for receiving signals by means of controlled fluctuations of a source of substantial- 1y invisible light, comprising a fluorescent screen means to collect and direct at least some of said light onto a part of said screen to energize said part into visible distinction, the center of said screen being of a diiTerent composition to afford a different appearance from the surrounding portion when the screen is so energized.

7. Apparatus for receiving signals by means of controlled fluctuations of a source of substantial- 1y invisible light, comprising a fluorescent screen, means to collect and direct at least some of said light onto a part of said screen to energize said part into visible distinction, the center of said screen being transparent when so energized to provide a sight on said source therethrough,

8. Apparatus for receiving signals from a source of substantially invisible light, comprising a fluorescent screen, means comprising a pair of reflectors to collect and direct at least some of said light each onto a part of said screen to energize said part into visible distinction, coincidence of said visible parts indicating a predetermined direction relative to said source.

9. Apparatus for receiving a signal from a source of substantially invisible light, comprising a fluorescent screen, means comprising a pair of reflectors to direct some of said light each onto a part of said screen, the relationship of said parts indicating the direction of said source from said apparatus said reflectors and said screen being arranged so that when the beam of invisible light is being followed by the reflectors and screen, the illumination from the two reflectors will be substantially superimposed on said screen to indicate correct direction of travel.

10. Apparatus for receiving a signal from a source of substantially invisible light, comprising a fluorescent screen, means to direct at least some of said light onto a portion of said screen to energize said portion into visible distinction, and means to make a visible index on said screen, the relationship of said portion and index inrespect to the screen, and will be in predetermined positions relatively to each other when the apparatus is pointed truly in the direction of the source.

12. Apparatus for receiving a signal from a source of substantially invisible light, comprising a fluorescent screen and a plurality of reflectors so arranged that the reflectors will each direct some of said light onto a part of the screen when the apparatus is pointed more or less in the general direction of the source, the parts of the screen so afiected will vary with the exact direction in which the apparatus is pointed with respect to the screen, and will be coincident when the apparatus is pointed truly in the direction of the source.

BROOKS WALKER. JOHN E. LINDBERG, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,310,852 Leverenz Feb. 9, 1943 1,149,123 Fuller Aug. 3, 1915 2,074,737 Wolfl Mar. 23, 1937 2,075,094 Chubb Mar. 30, 1937 2,334,085 Graves et al Nov. 9, 1943 2,199,066 Bernstein Apr. 30, 1940 1,335,520 Muller Mar. 30, 1920 1,385,657 Bell et al. July 26, 1921 1,936,514 Lengnick Nov. 21, 1933 2,032,588 Miller, Jr Mar. 3, 1936 2,062,512 I-Iine Dec. 1, 1936 2,120,765 Orvin June 14, 1938 2,225,044 George Dec. 17, 1940 FOREIGN PATENTS Number Country Date 352,035 Great Britain June 22, 1931 Great Britain Feb. 18, 1932 

